Plasmon polariton modes guided by a metal film of finite width

The properties of purely bound plasmon-polariton modes guided by a symmetric thin metal film of finite width are described for what is believed to be the first time, and a suitable mode nomenclature for identifying them is proposed. The dispersion characteristics of the modes as a function of film thickness are presented. It has been found that long-range plasmon-polariton modes exist in a symmetric film structure and that one of them may be suitable for optical signal transmission.